A number of social, psychological, and biological events co-occur during puberty, making this developmental period a time of stress for some and a time of rapid and multifaceted change for all. Previous studies of girls' psychological adaptation to pubertal development have not emphasized the endogenous and exogenous variables that mediate between biological change and psychological outcome nor have they examined girls' reactions to differential rates of pubertal progress, asynchronies in pubertal indices, or timing of maturational events, especially with regard to delayed puberty. Two hundred and twenty girls will be followed longitudinally, being seen twice a year for a four year span. One hundred and ten will be followed from fifth to eighth grade and 110 from seventh to tenth grade. Approximately one-quarter will be drawn from a sample known to be at risk for delayed puberty and asynchronies in physical development--ballet students in professional dance companies. The other three-quarters will be normal students from comparable demographic backgrounds. Current physical indices of pubertal status (Tanner staging, growth parameters), exogenous variables (peer referent groups, family relationships and stress, maternal attitudes about puberty), and endogenous variables (feelings about pubertal change, temperamental characteristics, body image) will be examined as they related to psychological adaptation (psychological adjustment, weight, and eating-related problems). In addition, the girls' activities and food intake will be assessed via 4-day diaries and 24-hour recall interviews. The major goals of the study are to examine: 1) physical, social & psychological precursors to eating-related behaviors in adolescent girls, 2) the antecedents to psychological adjustment in girls, 3) the relationship of pubertal status, especially delayed and asynchronous puberty to psychological functioning, 4) the developmental course & body size estimation in the adolescent girls and the factors that may influence the emergence of body image distortions.